The present invention pertains to communication methods and devices, and more particularly to an improved method and device for formatting a message.
The signaling frame (such as the DCCH frame in IS2000 systems) used to transmit a signaling message over a cellular system, such as a code division multiple access (CDMA) system or a time division multiple access (TDMA) system, typically includes a frame header, a message slot, a code redundancy check (CRC) etc. It is known for the message slot to have a predetermined length, and it is further known for the frame to have a predetermined length. For example, IS-95 and IS-2000, which are the current 2G and 3G CDMA standards in the United States, have a predetermined message slot length. On the other hand, signaling messages may have varying lengths and under the standard, the leftover space is not used. Clearly, for short messages the waste of resources can be significant. Table 1 lists different message sizes for IS2000 systems.
Table 1 assumptions: P_REV_IN_USE greater than =7, Encryption off, 3 Pilots visible to MS, DTMF burst of 10 digits.
As can be seen from the table, the messages have varying lengths, and the shorter messages do not use the full frame length. Accordingly, available bandwidth is wasted when shorter messages are transmitted.
The standard technique for recovering a message at the receiver is to check the frame CRC first after decoding the frame. If the frame CRC fails, the message is discarded, or erased. If the frame CRC is good, the message CRC is checked. If the message CRC fails, the message is discarded. Otherwise, the message is retained. Erased signal frames can translate into dropped calls, radio frequency (RF) power overruns, and user dissatisfaction. For example, when checking voice mail, keyed-in digits are sent over a signaling frame and the frame is erased. The phone display shows that the correct number was entered, but the user has to reenter them when the correct numbers are not received at the central server. Users can find such performance aggravating.
Accordingly, there is a need for an improved messaging format to enable more reliable communication.